Background: Uncertainty over the therapeutic benefit provided by parenteral remdesivir in COVID-19 has resulted in varying treatment guidelines. Early in the pandemic the monoclonal antibody cocktail, casirivimab/imdevimab, proved highly effective in clinical trials but because of weak or absent in vitro activity against the SARS-CoV-2 Omicron BA.1 subvariant, it is no longer recommended. Methods: In a multicenter open label, randomized, controlled adaptive platform trial, low-risk adult patients with early symptomatic COVID-19 were randomized to one of eight treatment arms including intravenous remdesivir (200mg followed by 100mg daily for five days), casirivimab/imdevimab (600mg/600mg), and no study drug. The primary outcome was the viral clearance rate in the modified intention-to-treat population derived from daily log10 viral densities (days 0-7) in standardized duplicate oropharyngeal swab eluates. This ongoing adaptive trial is registered at ClinicalTrials.gov (NCT05041907). Results: Acceleration in mean estimated SARS-CoV-2 viral clearance, compared with the contemporaneous no study drug arm (n=64), was 42% (95%CI 18 to 73%) for remdesivir (n=67). Acceleration with casirivimab/imdevimab was 58% (95%CI: 10 to 120) in Delta (n=13), and 20% (95%CI: 3 to 43) in Omicron variant (n=61) infections compared with contemporaneous no study drug arm (n=84). In a post hoc subgroup analysis viral clearance was accelerated by 8% in BA.1 (95%CI: -21 to 59) and 23% (95%CI: 3 to 49) in BA.2 and BA.5 Omicron subvariants. Conclusions: Parenteral remdesivir accelerates viral clearance in early symptomatic COVID-19. Despite substantially reduced in vitro activities, casirivimab/imdevimab retains in vivo antiviral activity against COVID-19 infections caused by currently prevalent Omicron subvariants.

Background Uncertainty over the therapeutic benefit provided by parenteral remdesivir in COVID-19 has resulted in varying treatment guidelines. Methods In a multicenter open label, controlled, adaptive, pharmacometric platform trial, low-risk adult patients with early symptomatic COVID-19 were randomized to one of eight treatment arms including intravenous remdesivir (200 mg followed by 100 mg daily for five days) or no study drug. The primary outcome was the rate of viral clearance (estimated under a linear model fit to the daily log10 viral densities, days 0-7) in standardized duplicate oropharyngeal swab eluates, in a modified intention-to-treat population (mITT). This ongoing adaptive trial is registered at ClinicalTrials.gov (NCT05041907). Results The two study arms enrolled 131 patients (remdesivir n = 67, no study drug n = 64) and estimated viral clearance rates from a median of 18 swab samples per patient (a total of 2356 qPCRs). Under the linear model, compared with the contemporaneous control arm (no study drug), remdesivir accelerated mean estimated SARS-CoV-2 viral clearance by 42% (95% credible interval [CI] 18 to 73). Interpretation Parenteral remdesivir accelerates viral clearance in early symptomatic COVID-19. Pharmacometric assessment of therapeutics using the described method can rapidly and efficiently determine in vivo clinical efficacy.

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